Primary Study On The Calcium Carbonate Crystal Metastable Region In The Circulating Cooling Water

In order to study the calcium carbonate scale and scale inhibition of the circulating cooling water, the variety of the pH value, absorbency and the Ca²⁺ concentration of the different concentration Ca²⁺ and HCO₃^- solution in different temperature are determined in the self-made crystal ware, which is in the absorbency process adding three different categories and different concentration scale inhibition agents. Different concentration of Ca²⁺; 3.192mmol·L^-1 6.000mmol·L^-1 ,12.01mmol·L^-1 and 20.01mmol·L^-1 are contained in the experimental solution. ATMP,HEDP and PBTC are used as the adding scale inhibition agents. 1 A device was self-made for observing the crystal pocess.2 The width of calcium carbonate crystal metastable region is determined by using the critical pH method. The width of metastable region with adding scale inhibition agent is more wide than it without the scale inhibition agent. The same concentration ATMP,HEDP and PBTC are added to the solution of Ca²⁺: 3.192mmol·L^-1 ,6.000mmol·L^-1 . Through the experiment, the effection of adding HEDP is good. While these three scale inhibition agents are added the solution of Ca²⁺: 12.01mmol·L^-1 ,20.01mmol·L^-1 , the effection of adding ATMP is good.。3 A series of solution of Ca²⁺: 6.000mmol·L^-1,12.01mmol·L^-1 and 20.01mmol·L^-1 are added the different concentration ATMP in 45℃, the connection of the Ca²⁺ concentration and the scale inhibition agent concentration is gained in the end. If knowing the Ca²⁺ concentration of the fact water in theory, the adding scale inhibition agent concentration which can made the solution reach the desired pH value can be figured out. 4. The diversification of the absorbency value of the calcium carbonate crystal process is determined by the spectrophotometer. The wavelength of 450nm is selected. Both after and before adding the scale inhibition regent, the change of the absorbency value is obviously, the extension of the sudden change and the descend trend of the pH value are same. This method can be as a good way to observe the crystal process. 5. The pH value and the Ca²⁺ concentration determined at the same time are made on the same chart. The changes are almost synchronous in the experimental solution without inhibition agent. But in the experimental solution contained inhibition agent, the change of Ca²⁺ concentration is not synchronous as the other two.